Submersible barge



Feb. 13, 1968 TAMIRO WATARI SUBMERS IBLE BARGE Filed April e, 1966 3 SheetsShee l wm. mm QN mm. o WW\ Nlmudlmw.

INVENTOR.

TAM/RO W TAR/ Wwf? @QL TTOENYS Feb. 13, 1968 TAMxRO WATARI SUBMERSIBLE BARGE 3 Sheets- Sheet 2 Filed April S, 1966 wmmw WNY w INVENTOR.

v TAM/R0 WATAR/ Feb. 13, 1968 TAMIRO WATARI SUBMERSIBLE BARGE Filed April a, 1966 3 Sheets-Sheet 5 INVENTORg, TAM/R0 WA TAR/ United States Patent O 3,368,512 SUBMERSIBLE BARGE Tamiro Watari, Kobe-shi, Japan, assigner to Continental Oil Company, Ponca City, Okla., a corporation of Delaware Filed Apr. 8, 1966, Ser. No. 541,334 Claims priority, application Japan, Oct. 30, 1965, Litl/66,647 4 Claims. (Cl. 114-74) ABSTRACT OF THE DSCLGSURE Apparatus for transporting large quantities of hydrocarbon products under water, the apparatus consisting of a water-tight vessel which is constructed with predetermined compartmentation such that end compartments of the vessel are constructed to be fluid-tight while central compartmentation is constructed to be air-tight, and the compartmentation as between the end compartments and the center compartments is volumetrically proportioned such that the buoyancy of the vessel is the same when either (a) all compartments are filled with hydrocarbon cargo or (b) the end compartments are occupied with sea water and the center compartment is maintained void.

This invention relates generally, as indicated, to a submersible barge; and more particularly, but not by way of limitation, to a submersible tow vessel for use in transporting crude oil.

The prior art reveals a few instances of teachings to the general concept of submarine towage but, prior to this invention, no practical method or equipment has been devised.

it was found that transport by submersible barge could be desirable for moving large quantities of crude oil, especially if the same transport route is run at regular intervals. The submerged tow encounters much less resistance during its use than would any of the known types of surface transport barges. The first advantage is that the submerged barge encounters no sea resistance from surface turbulence, e.g., waves, wind, etc. This detriment can be very great and tends to reduce greatly the maximum tow-speed which can be achieved with surface hauling equipment. The surface barge can be towed at only a few knots, if given good sea conditions, while the submerged barge, as presented herein, can be hauled at speeds up to around sixteen knots. Further, even with this diiierence in tow speed, the towing force required of the hauling ship is still considerably less in the case of the submerged tow than it would be with a dredge-type barge of comparable size. Thus the present invention enables a faster tow with less towing force.

The submerged barge concept is also attractive from the cost viewpoint, both in manpower and in maintenance. The submersible vessel of this invention is designed so that no manpower is required at any time during the voyage or when left to await loading or unloading. Also, the vessel enables savings in docking fees since it requires no port facilities while tied up or anchored out. ln one planned usage, the unmanned, submersible barge can be fully loaded with cargo and then hauled at standard speed by a fully loaded tanker or cargo ship, as opposed to a sea going tug, to a first port of call. The barge can then be dropped oli at the first port and the tanker or cargo ship can proceed to another destination with its remaining cargo.

The present invention contemplates a submersible tow vessel containing cargo holds of predetermined volume and pressure-resistance capabilities which maintain the vessel at the same buoyancy when they are either (i),

ice

filled with cargo, or (ii) occupied with proportionate amounts of sea water and gas, such as air. In a more. limited aspect, the invention contemplates a submersible hull member outfitted with suitable ballast tanks and having multiple cargo hold spaces; a portion of the cargo hold spaces being nonpressure-resistant, of predetermined volume, and located in a balanced relationship with respect to the center of buoyancy of the hull; and additional cargo hold space which is pressure-resistant, of predetermined volume and also balanced with respect to the center of buoyancy of the vessel. The pre-determined volumes being such that the buoyancy of the vessel will remain the same when (i) all holds are filled with crude oil or (ii) the nonpressure-resistant and pressure-resistant hold spaces are occupied by sea water and air, respectively.

It is an object of the present invention to provide a submersible barge for carrying large amounts of cargo.

It is another object of the invention to provide a submersible barge having particular compartmentation and which can be towed at relatively high sea speeds while either loaded with cargo or unloaded.

It is a further object to provide a submersible tow vessel for carrying large amounts of crude oil which requires no personnel in attendance either underway or when tied up.

It is another object of this invention to provide a submersible barge wherein the weight of the vessel, its hold compartmentation, and its overall volumetric specifications are built in accordance with design criteria found to yield the best possible hydrodynamic characteristics in the towing attitudes.

it is still another object of the present invention to provide a submersible barge which has a single preset amount of buoyancy both in the transport phase of the voyage when all holds contain crude oil cargo, and in the return phase when a given number of nonpressureresistant holds are filled with sea water and a remaining pressure-resistant hold is maintained void.

Finally, it is an object of the invention to provide a. submersible barge capable of fast, low cost crude oil transportation which maintains maximum towing efficiency during all phases of sea travel whether loaded or unloaded with crude oil cargo.

Other objects and advantages of the invention will be evident from the following detailed description when read in conjunction with the accompanying drawings which illustrate the invention.

In the drawings:

FlG. 1 illustrates a preferred form of cargo hold spacing to be compartmented in the submersible barge.

FIG. 2 is a side view of the preferred form of the barge in yvertical section.

FG. 3 is a section taken along line 3 3 of FIG. 2.

FIG. 4 is a section taken along line 4 4 of FIG. 2.

FIG. 5 is a section taken along line 5 5 of FIG. 2.

FIG. 6 is a section taken along line 6 6 of FIG. 2.

FIG. 7 is a top plan view of the preferred form of submersible barge.

FIG. 8 illustrates an alternative form of compartmentation.

FIG. 9 illustrates a second alternative form of compartmentation.

General and theoretical The invention of this disclosure hasa in one instance, been specically designed for use in transporting crude oil in the Mediterranean Sea; however, it should be understood that the design parameters may be varied for any particular usage and/ or area. The submersible barge, as described herein, has a principal function of transporting crude oil from a source port to a refinery and then the barge is returned to the source port to rell and repeat the run.

There are many obstacles to be overcome in constructing a submersible barge which can be reliably towed with acceptable eiciency. Heretofore, the theoretical designs which have been recorded were very basic disclosures having neither the awareness of the problems to be encountered nor the scope of experimental findings which would enable a solution to the various problems. The design as set forth in this disclosure is the result of wind tunnel and sea tests which have provided the empirical data and hardware knowledge which allow construction of a highly etlicient transport vessel that is capable of moving cargo via the water subsurface at greatly increased speeds.

The submerisible barge as disclosed herein has been designed with a specific shape and weight such that the best and most stable operating characteristics are achieved. The craft is balanced and ballasted so that it will have a known function of movement and it will travel in an equilibrium condition when under tow. That is, that given the proper amount of cargo, and when the craft is then properly ballasted and trimmed, the towed submersible barge will travel in a desired pattern without any necessity for further direct control. The barge can then be controlled to a sufficient degree by the speed of tow and/or the length of the towline.

The submersible vessel dpends upon exact conditions for the equilibrium behavior; hence, when the vessel is loaded with a known amount of cargo it must be properly ballasted and trimmed before getting underway. The design criteria established that a reserve buoyancy of fty (50) tons to the fully loaded barge will give consistent results as to towing efficiency and reliability. The barge, loaded and ballasted, does not sink entirely below the surface of the water, but rides with a very small freeboard. Then, upon getting underway, new forces enter in to submerge and stabilize the barge in the desired manner.

When the speed of tow approaches about nine (9) knots, the barge will start to submerge and will continue to submerge as a function of the speed of tow and/or the length of the towline. The submergence force is a resultant of (l) drag due to frictional resistance of the hull, (2) lift forces of wings and hull (a depressive force in this case), (3) tension of the towing wire at the connecting point to the barge, and (4) the reserved buoyancy of the barge. These same forces act about their respective moment centers and combine to an equilibrium condition of their resultants at a given tow speed and towline length. With this particular barge design, considering the loaded weight and the adjusted reserve buoyancy of iifty (50) tons, it has been found that a tow ship cruising at fourteen and one-half (141/2) knots with a tow line of 300 meters will maintain the submerged barge cruising in its equilibrium condition at a depth of about twenty-ve (25) meters.

This then gives rise to three more considerations which must be decided in order that the ensuing design parameters will be properly proportioned and/or weighted. First, the mean specific gravity of the water in which the vessel will operate. This was found to be 1.030 for the central Mediterranean area. Second, the specific gravity of the crude oil to be carried by the vessel, and this was found to be a value of at least 0.84 for crude oil shipped from the source port. Thrid, the depth of water through which the submerged barge travels. The safe minimum for this depth is fty (50) meters and a suitable sealane can be established.

Investigation of underwater towing with vessels of large size has shown that the buoyancy of the vessel is an extremely sensitive factor. The specific gravity of sea water will vary with changes in salinity and/or temperature and it has been found that when passing through a gradient of specific gravity change the stability of the vessel is varied by an inordinate amount. The specific gravity of the cargo then enters into the consideration and the empirical findings support a design which strikes a balance as to' the optimum size of the barge with regard to the buoyancy effects to be encountered.

Under the conditions anticipated above, i.e., sea water specific gravity of 1.03 while the crude oil specific gravity will be not less than 0.84, the following dimensions were found to be consonant with the best operation of a submersible vessel 10 as shown in FIG. 1.

Meters Length (main hull) 72.2 Length (overall) 75.2 Breadth 12.0 Depth (main hull) 12.0 Depth (overall) 15.15

These dimensions result from considerations of the desired volume of cargo and ballast space to be disposed within a submersible barge of the type as disclosed herein.

In FIG. l, the hull or skin 20 of the vessel 10 is shaped as a streamlined body of revolution having a parallel niidbody. A ballast keel 21 is formed on the underside of hull 20 and is loaded with either solid or liquid ballast of that desired weight which is necessary to secure stability of the barge. The barge is designed so that, when fully loaded with, cargo properly ballasted to have a reserve buoyancy of fty (50) tons, and trimmed, the vessel 10 will iioat at the surface of the water with only the fairwater 22 and about one (1) meter of freeboard extending above the surface.

The barge is then taken down to its cruising depth by the force of the forward towing movement as exerted by the tow line 24, a suitable cable. As the vessel 10 approaches nine (9) knots, the increasing water drag along the bottom of the hull 20 acting with the force of forward tow about the center of the reserve buoyancy, tends to tilt the vessel 10 forward and it'submerges. The lift force of depression from bow wing 26 is also instrumental in the accelerating or diving condition and tends to aid the submerging resultants. The vessel 10 will then come to an equilibrium condition at a predetermined depth which is a function of the vessels speed and towing angle (length of towline). The vertical tin 23 and the stern wing 25 provide stability to the craft after it reaches the equilibrium condition; that is, the proper depth, speed and attitude for standard speed towing.

The proper volume of the vessel 1t), which is a function to be considered relative to the physical size of the vessel and the towing requirements, must be such that a denite desired amount of buoyancy results when the vessel 10 is completely loaded. The cargo tanks 27 and 28, after and forward, respectively, are built to be non-pressure-resistant and the central cargo tank 30 is of pressure-resistant design. The reason for this will become apparent. Complete loading is of great importance so that there can be little or no shifting of weight within the vessel 10 at any time when it is underway. Therefore, each of the nonpressure-resistant cargo holds or tanks 27 and 28 and the pressure-resistant cargo hold or tank 30 must be of a l proportionate total volume in order to interact with other buoyancy and gravity forces of the vessel 10 to allow the attaining of equilibrium conditions. Also, the various ballast and trim tanks (to be described) must be of proper volume as dictated by the operational requirements.

A further parameter controlling the size of cargo tanks 27, 28 and 30l is the specic gravity of the cargo crude oil (.84) and the allowed mean sea water (1.030). The barge is designed to enable the proper reserve buoyancy of 50 tons, as required by considerations of the size and dead weight of the vessel and the chosen towing characteristics (speed, cable-length and depth), when the cargo tanks 27, 28 and 30 are totally filled and the necessary ballast and trimming conditions are met. Further, the volume of the cargo tanks is adjusted to provide a balanceable relationship as follows. On the loaded (cargo) voyage, the three sign conditions and enable the proper reserve buoyancy to be imparted to the vessel. On the return voyage, the tank volumes are apportioned so that when the nonpressure-i resistant tanks 27 and 28 are completely filled with sea water, having the greater specific gravity of 1.030, and the pressure-resistant tank 30 is maintained void (filled only with air at substantially atmospheric pressure), the vessel 1f? will still have the same reserve buoyancy and will respond to towing in the same manner.

Description of the invention Referring to FlG. 2, there is shown a preferred design of the vessel 10, the design having compartmentation which adheres to the dimensions and weights referred to in this specilication. As previously indicated, the vessel 1i) is formed with a hull (skin) Ztl, a streamlined body of revolution, and the appertinent external stabilizing and controlling members. The hull 20 is compartmented to provide the three watertight and oiltight cargo holds or tanks 27, 23 and 30. Tank 27 is a nonpressure-resistant cargo tank and is formed by the hull 26, after bulkhead member 32, and forward bulkhead members 34 and 36, and the tank is strengthened by a series of spaced transverse stilening members 38. The forward nonpressureresistant cargo tank 28 is formed by hull Ztl, supported and strengthened by transverse web members 38, and bulkheads 4t), 42 and fifi. The midships cargo tank 30 is pressure-resistant (shown as a double line) as formed in hull 20 between the transverse bulkheads 36 and 44 and above a deckplate 46. The pressure-resistant tank 3G is airtight and itis strengthened by a plurality of transverse web members 48 which also extend below and serve to minimize ballast motion in the underlying auxiliary tank Sti as will be shown in connection with FIG. 4. The main longitudinals 51 and 53 support the transverse members 38 in the cargo tank spaces 27 and 23.

Ballast tanks are located fore, aft and amidships in the vessel 1t! and each tanks capacity is designed in keeping with the overall size and buoyancy which is necessary to enable the desired tow characteristics. The forward main ballast tank 52 (also see FIG. 3) is formed in the hull 20 between transverse -bulkhead members d@ and 54 and the deckplate 56. The longitudinal member 5S serves to strengthen the tank. Beneath the deckplate 56 is the forward trim tank 6), a pressure-resistant space (double line) as bounded by hull Ztl, deckplate 56 and the lower portions of bulkheads 4t) and 54. The longitudinal web 62 serves as a strengthener.

Referring to FIG. 3, there is shown a section along lines 3--3 of FIG. 2 which shows the cross-sectional configuration of ballast tank 52 and the pressure-resistant forward trim tank 60. The side portions 64 of deckplate 56 are bent downwardly and welded to the skin or hull 22 to thereby define the trim tank 6) as an airtight, pressure-resistant enclosure. Flood holes 66 are provided on i each side of the hull 2Q at the lower sides (port and starboard) of the main ballast tank 52. The holes serve for entry and exit of sea water during the ballast venting and ballast blowing control functions. The trim tank capacity is controlled by dockside pumping facilities and therefore no provision is specified for flood control.

An auxiliary or midships trim tank Sti is provided beneath the pressure-resistant cargo tank 3] and centered on the ballast keel 21. FG. 4 shows the midships tanks in cross-section as taken at 4-4 of FiG. 2. The hull Ztl and transverse webs t8y define the pressure-resistant (double line) shell with the bent deckplate 46 forming an oiltight separation between cargo tank 30 and midships trim tank 50. A longitudinal stiffener 68 is placed in the center of trim tank Sti and is provided with holes 70 (see FIG. 2) for water passage between the port and starboard sections of the tank.

The after rnain ballast tank 72 and after trim tank '74 are formed by the transverse bulkheads 32 and 76, the hull 2t) and the reinforced deckplate 7S. The after trim tank 74 is also made pressure-resistant; hence, it should be apparent that any interior space which may be rendered filled or partially filled with air or void during submerged voyage conditions is formed to be airtight and pressure* resistant up to the largest rated operating pressures plus a percentage for safety factor. This has been specied as the pressure at sixty (60) meters of sea depth. FIG. 5 shows the after tanks in section as taken at lines S-S of FIG. 2. The after main ballast tank 72 is provided with transverse webs to support the outer skin or hull 20. Flood holes 82 are provided on the port and starboard lower sides of ballast tank 72 for sea water control, i.e., flooding and blowing of the ballast tanks. Suitable longitudinal stilfeners 84 are provided to reinforce the ballast enclosure. The downwardly bent deckplate 73, of pressure-resistant construction, separates off the volume of the after trim tank 74. A longitudinal member 86 having water passage holes 88 (FIG. 2) supports and strengthens along the center line of the trim tank 74.

Spaces 90 and 92 near the middle of the vessel (FIG. 2) each comprise a pair of tanks, a collection and an expansion tank, which work in conjunction with the respective, adjacent nonpressure-resistant cargo tanks 27 and 28. In the stability equation for the vessel, the volume of spaces 9i? and 92 must be considered as part of the volume of cargo tanks 27 and 23 since each respective pair is'in liquid communication. Actually in each respective set of tanks, the expansion tank volume will constitute four percent of the volume of its respective nonpressure-resistant cargo tank and the associated collection tank will amount to about three percent of the volume of the same cargo tank.

The expansion and collection tanks are arranged in sid-e-by-side relationship as shown in FG. 6, a section from lines 6-6 of FlG. 2. The hul-l 20 is braced by a transverse stiffening member 94 which also serves as the lower panel of expansion tank 96 and collection tank 98. A vertical panel member litt) completes the bounds of the expansion tank 96 so that it is watertight from both the cargo tank 2S and the collection tank 98 with the exception of a pipe 102 which opens at the topmost part of the expansion tank 96 and extends down to the bottom of cargo tank 28. A suitable strainer or rose'boX M24 is placed on the bottom end o-f pipe 102. The collection tank is bounded by hull 2t), transverse plate 94 and a rising panel 106 which is open at the top; hence, the collection tank 98 is in direct communication with the cargo tank 28 through suitable openings at point 16S in the transverse plate 94.

A flow direction panel 11) is atixed at the top of hull 2th and placed parallel to the rising panel 106 thus forming a flow trap for liquids owing between the collection tank 98 and the cargo tank 28.

A bidirectional ow line 112, for hook up to dockside facilities, communicates through a stop-valve 114 to the opening 116 at the top of the collection tank 98 and serves as the oil flow line for either loading or unloading, as will be explained later. A second coupler line 118, controlled by a stop-valve 120 extends down to a bell mouth suction head 122 which is placed on the bottom panel 94 of the expansion tank 96. The line 118 is a sea water line and is also bidirectional depending upon the phase of operation, i.e., loading or unloading of crude oil cargo. The valves and control access are disposed within the fairwater 22 as illustrated.

The expansion and collection tanks find their primary function in the cargo loading and unloading process as will be described in the operation section of the specification. Also, when the vessel is loaded and underway the expansion tank supplies a reservoir wherein, in the event of a degree of expansion in the bulk of the crude oil cargo, due to temperature change, etc., the pressure is relieved by forcing crude oil into the expansion tank with the consequent displacement of sea water to the exterior. Hence, no crude oil is lost into the surrounding sea.

Referring again to FIG. 2, the bow and sterm comprise nonwatertight compartments 126 and 1.28. Each of these compartments is formed by the hull and bulkheads 54 and 76 and each has suitable structural strengthening members, transverse, and longitudinal, which is characteristic of the design type. Also, it should be obvious that the plating of hull Ztl is of reinforcing thickness at all areas bounding pressure-resistant spaces (double lines).

The bow wing 26 and stern wing Z5 is each suitably mounted on the hull and provided with adjusting mechanism. The adjusting mechanism may be a suitable manually controlled hydraulic device since the wing adjustments are made in port, before towing is underway, for the entire voyage. The bow wing 26 has a connecting linkage 130 which extends through cargo tank 28 and hull 29 to a space in the fairwater 22 wherein the adjustment mechanism 132 is located. The stern wing 25 is controllable through a linkage 134 from an adjusting mechanism 136, located high up in the vertical iin 23. The location of the adjusting mechanism 136 is easily accessible when the vessel JP is at rest in a port or mooring facility. After the wing members and 26 have been set previous to getting underway, they may be left at that setting for the entire voyage or voyages.

The vessel 11i requires extensive piping, valving, etc. for enabling control of liquid cargo. The fairwater 22 encloses the necessary air pressure sources 149. This is a figurative showing and actually a bank of many of such compressed air containers is secured in the fair water 22. Also, in the fairwater 212, there is a pressure-resistant container 142 which houses and protects batteries in section 144, radio control equipment in section 146, and electromagnetic valves for blowing and venting ballast are contained in compartment 148. The vessel has provision for radio control of certain functions as will be described. The electromagnetic valves in compartment 148 can be actuated either by radio when the vessel 1t) is on the surface or by a pressure switch safety mechanism (at a predetermined maximum allowed depth) to blow the ballast and cause the vessel to rise. A suitable antenna 149 in conventional submarine mounting is located on the fairwater 22 and in electrical connection with the radio equipment in section 146. It is also planned that the radio equipment space 146 contain further electronic equipment such as; a transmitter for surface indication, indicators for sea water and oil level, and radio controlled towline release equipment.

The piping and valving of the vessel, control of which is located in fairwater 212, is quite extensive and it is not shown since the particular layout and control is not part of 4the present invention. The nonpressure-resistant tanks 27 and 28 are adapted to contain either sea Iwater or crude oil depending .upon the phase of operations. This is best described with reference to FIG. 6. In the cargo unloaded condition, the cargo tank 28 will be full of sea walter. To load crude oil, the line 1112 lis connected (at the dockside facility) to supply an input of crude oil through valve `114 and outlet `1116 into Ithe collection tank 98. The collection tank 98, having also been lled with sea water :at the start, increases its crude oil content (from top tto bottom), thereby forcing, first se'a water `and then crude oil through the trap, over panel 106 and down through openings '108, into the main body olf lcargo Itank 28. Simultaneous wit-h this action, the dockside line 118 is withdrawing sea water from the bottom of expansion tank 96 which in turn draws replacing sea water, via the pipe 102 and rose'box 104, from the bottom olf cargo tank 28. Since cru'de oil and sea water are imm-iscible liquids, the sea water can be efficiently withdrawn from the ybottom while cru'de oil is supplied at the top. When tank 28 'is full, an'd 'a first present amount of crude oil is detected entering the expansion tank 96, the tank filling operation is :ceased and :the cargo tank 28 is ready for voyage. This leaves a small amount of sea water remaining in the expansion tank 96, and in the event of a condition underway which causes expansion of .the crude oil, the crude oil can expand into tank 96 and displace sea water through a suitable relief valve (not sho-wn) into the exterior sea water. In 'this manner, there are no pressure variations exerted from the cargo volume and there is nto loss of cargo in the process of relieving the pressure.

In the cargo unloading phase of operation, the 'pipes 112 and i118 are merely connected or valved at dockside for reverse function. Sea water is pumped into the expansion tank 96, with consequent overflow 'to the *bottom of cargo tank 28, while crude oil is being pumped out of the collection tank 98 via the outlet 116 and pipe 112. The sea water w-ill float the crude oil all |the way to the top corner of collection tank 98 and with proper detection measures the `unloading openation is stopped to leave the tanks totally iille'd with sea water. This amount of sea water will be the proper volume vfor enabling a precise lballasting of the Vessel 10 on its return voyage. The stern cargo tank 27, vbeing of the nonpressure-'resistant type, is loaded an'd unloaded in the same manner.

With the midships cargo tank 30 the procedure must be different. The tank S0, a pressure-resistant tank, will contain crude oil on the payload trip ibut it must 4be maintained void on the return. Hence, when loading, the crude oil is pumped Idirectly into the tank 30 and it is provided with a suitalble pressure relief at the to-p. In unloading, a conventional suction mouth pipe (not shown) is connected to draw 4crude oil from the bottom ofthe cargo tank 30. At the `same time a tbooster supply of air pressure is intro-duced at the top of tank 30. This booster air is of medium-high pressure, about 1.5 kg./cm.2.

While loaded with cargo and underway, the cargo .tank 39, as well as tanks 27 and 28, are supplied with suitable venting means which provide gas or fume escape through a conventional flame-arresting relief head (not shown).

The main ballast `tanks 52 and 72 are filled and evacuated by conventional pneumatic control. When filling, .the air within the ballast tanks is vented to allow sea water to come in through the flood holes 66 and 32. See FIGS. 3 and 5 showing sections of the forward and after ballast tanks, respectively. The ballast tanks are filled for both the payload and the return voyage. A high pressure cornpressed air source, 3() kg./cm.2, is utilized for evacuation by introducing the air in the top area of the ballast tank and forcing the sea walter out through the flood holes. A Ipressure responsive safety device (not shown, is utilized for initiating the automatic blow oli or evacuation of ballast when the vessel exceeds a preset subnormal depth.

The trim tanks, forward trim tank60, after tank 74, and the 'auxiliary midships tank 50 are e'ach pressureresistant and are each filled with sea water from docks-ide lines. It is also contemplated Eto include intra-vessel pipes between the trim Itanks for ballast adjust-ing purposes. Primarily, however, 4.the trim tanks can each be iilled to a proper ballasting volume trom a dockside or other metered supply o-f sea water. Evacuation ofthe trim tanks requires booster air pressure coupled with sea water suction in the manner prescribed for the pressure-resistant cago tank 30.

Manholes (FIGS. 2 `and 7) are provided throughout the yvessel for cleaning and access. Also, ladders and steps (not shown) are presen-t in all interior spaces. The necessary mooring and handling facilities are located on the fairwater 22. The bollards `152 and closed fair leadens 154 prov-ide fore and `att mooring devices, and it should be understood lthat other devices for spring-like, or 'whatever mooring configuration, can be attached. A towing eye 156 is provided on lthe upper bow portion of the hull 20. This is a towing point which can give good results but it should be stated that `the point of tow can be anywhere from the exact bow point or center on black to about 'the beginning of fairwater 22, as long as the proper adjustment is made for the inclination of lbow wing 26.

FIG. 7, a top view of the vessel 10, shows several of the features to better advantage. In .the fairwater 22, -t-he compressed air containers 14) are aligned in parallel banks. Other suitable valving and pneumatic control devices (not shown) would be located in the fairwater. The electromagnetic valves which control the high pressure ballast tank supply are located in compartment 148 within lthe pressure-resistant space 142. Also, in the shell of pressure-resistant space 142, suitable watertight venting means 11518 are provided for 'the compartments 1416 and 144 which contain the radio control gear and batteries, respectively.

Operation The description of operation will proceed with reference to FIG. 2 unless otherwise noted. The vessel 1t) is first loaded with crude oil. This entails either pumping or gravity fill of crude oil from dockside storage into the three cargo tanks. The loading of crude oil into the nonpressure-resistant tanks 27 and 28 will also require simultaneous pumping out of sea water from the lower limit of the tanks 27 and 23 as previously described. When a predetermined amount of oil has been detected within the expansion tanks 96 and 160 (see FIG. 7) the loading is ceased as the proper capacity has been reached; that is, the respective collection tanks 98 and 162 and cargo tanks 28 and 27 will be filled with crude oil, and the expansion tanks 96 and 160 will contain some crude oil but also a suiicient volume of sea water. This suicient volume will adhere to the ballast stability equation of the vessel and will provide a small quantity of sea water for dispelling from the tanks in response to any expansion of the crude oil cargo.

The midships cargo hold, pressure-resistant tank 30, also receives its full volume of crude oil from the dockside source and venting or air evacuation means is provided to allow lling of the pressure-resistant tank Btl. This completes the cargo loading and each of the cargo tanks 27, 2S and 3d is completely filled with a predetermined volume of crude oil having a known specific' gravity.

Next the vessel 1) is properly ballasted and trimmed for submarine travel. The Afore and aft ballast tanks 52 and 72, respectively, are maintained to be lled with a volume of sea water. This is done by venting the air within the ballast tanks and allowing a required amount of sea water to ood the respective chambers of the ballast tanks 52 and 72. Next the vessel 10 must be trimmed to maintain fore and aft balance and to compensate for overall weight and/or buoyancy change of the Vessel. The fore, aft and midships trim tanks 60, 74 and 50', respectively, are each connected to a dockside or other available source of compensating sea water. The compensating sea water is pumped into the pressure-resistant trirn tanks, with simultaneous venting of air from the tanks, until the proper trimming of ballast is achieved; i.e., a reserve buoyancy of fifty (50) tons. In most cases the desired trimming will require a predetermined volume of sea water (of known specific gravity) in each trim tank and this can be determined by suitable ow meters measuring the input of compensating sea water to each of the trim tanks.

When proper trimming is achieved, the vessel will have the proper buoyancy, about 50 tons of reserve buoyancy, and it will have the designated centers of both gravity and buoyancy, such that stable undersea towing can be carried out in accordance with the required parameters of the operation. When the loaded, ballasted and trimmed vessel sits dead in the water, the major portion of the vessel is underwater; only the fairwater 22 and the top of vertical fin 23 will be showing above the waters surface. As forward towing commences the vessel remains at the surface up to a speed of nine (9) knots. Above nine (9) knots the vessel 1t) will submerge and move deeper .proportional to its speed of travel until it reaches the desired cruising depth. This cruising depth is regulated by a particular static setting of bow wings 26 (which are preset at a port facility and then left alone) as they function jointly with the length (angle) and speed of tow, the water resistance of the vessel, and the reserve buoyancy, so that the vessel will cruise stably at the proper depth. It is desirable to provide a towline of about 300 meters length and a towing speed of 141/2 knots. This will then tow the vessel 10 at a depth of about 25 meters as measured from the water surface to the towpoint on the vessel (towing eye 156).

It has been found that changes in salinity, temperature and/or specic gravity can cause unusually large depth variations in submersible barges. The vessel of the present invention is designed to minimize these effects, since it is positively ballasted to be at the surface when at rest, but in the event of great depth variation, automatic pressure switch means is provided to blow ballast at a predetermined depth as decided by the depth rating factors of construction.

When entering port, or channels approaching thereto, the vessel automatically rises to a lesser cruising depth with reduction in speed. When the speed falls below about nine (9) knots, the vessel 1t) surfaces and travels with the fairwater 22 exposed and it can then receive radio control signals from the tow ship via the antenna 149 which actuates the appropriate radio control and electromagnetic valves (not shown) located in spaces 146 and 148, to blow all ballast from tanks 52 and 72. This raises the vessel further out of the water and serves to enable better port maneuverability and servicing access.

Cargo is unloaded by pumping oil out of the cargo tanks. In the nonpressure-resistant cargo tanks 27 and 2S sea water is simultaneously pumped in and the crude oil iloated out. In the pressure-resistant tank 30, air is pumped in and the crude oil is suctioned out from the bottom of the tank. When the unloading operation is completed, the nonpressure-resistant tanks 27 and 2S will be illed with sea water, and the pressure-resistant tank 30 will be void; the ballast tanks 52 and 72 can then be reooded and the entire vessel will have the same reserve buoyancy and force moments of operation as in the cargo loaded condition. The return voyage can then be made under the same speed and tow conditions, and the submersible vessel 10 will have the same stability and operating parameters. Thus, by precisely proportioning the volumes of the cargo tanks in accordance with the specific gravities of crude oil and sea water, the same stability of operation is maintained on both the payload and return voyages.

The volumetric capacities of the tank equipment in the specific design of this invention are as follows:

Cubic Meters Cargo oil tanks 5,810 Collecting tanks Expansion tanks Ballast tanks 300 Trim tanks 245 It should be understood, however, that larger or smaller craft can be designed which will afford the same reliability and behavior under the various tow conditions when all parameters of the design are proportionately changed.

Alternative 'embodiments FIGS. 8 and 9 show skeletal sections of alternative submersible barge devices which could -be built with adherence to the design characteristics of the present in- Vention. The compartmentation could be varied in several ways so long as the force moments, buoyancy, etc. of the submersible vessel are kept equal, and the volumetric considerations of the pressure-resistant and noupressureresistant tank spaces are kept proportional to the specific gravity differentials which will be applicable; i.e., the difference between sea water and crude oil as disclosed herein. FIG. 8 shows a submersible barge 170 having alternate pressure-resistant tanks 172 and 174 situated between the nonpressure-resistant tanks 171, 173 and 175. Ballast, trimming and piping equipment would be similar to that of the preferred embodiment. In FIG. 9, the submersible barge is shown as having two axially concentric cargo tanks of the necessary proportionate volume. The outer tank 181 is shown to be the nonpressure-resistant tank, while the inner tank 182 is pressureresistant. Other forms of tank layout could be constructed in keeping with the overall design considerations of the invention.

The specification has set forth a novel submersible barge design which is capable of being towed reliably at high speeds. Further, the submersible vessel of the invention can carry cargo loads of a size which, heretofore, was considered beyond practical lbounds in any type of underwater transport. The invention sets forth novel weight distribution and ballasting techniques which serve to maintain the craft stable under tow at all times whether on a payload or deadhead voyage. The design is particularly suited for crude oil transport of the pattern where regular runs are made over the same sealane. Under such conditions the round-trip voyage can be made with a minimum of expense and delay `and at a much greater sea speed than has heretofore been possible with towed vessels.

Changes may be made in the combination and arrangement of elements as heretofore set yforth in this specication and shown in the drawings; it being understood, that changes may be made in the embodiments disclosed without departing from the spirit and scope of the invention as defined in the following claims.

I claim:

1. A submersible vessel for transporting -a crude oil cargo between a source port and ya receiving port and for returning to the source port without cargo, comprising:

a hull member;

keel means imparting a predetermined ballast;

ballast tank means imparting a further predetermined controllable ballast;

rst and second nonprcssure-resistant cargo hold means disposed in said hull in a balanced relationship with respect to the center of buoyancy; and third pressure-resistant cargo hold means disposed in said hull in a balanced relationship with respect to said rst and second hold means; each of said rst, second and third hold means being volumetrically proportioned so that the vessel buoyancy when all hold means are filled with crude oil is the same as when the nonpressure-resistant hold means are filled with sea water and the pressureresistant hold means is void. 2. A barge as set forth in claim 1 which is characterized further to include:

trim tank rneans located extremely `fore and aft and amidships in the hull member. 3. A barge as set forth in claim 1 wherein said ballast tank means comprise:

main ballast tanks located fore and aft for controlling the buoyancy of the barge; Iand trim tank means located fore, aft and amidshps for balance control of the buoyancy of the barge. 4. A barge as set forth in claim 3 wherein said main ballast tanks include:

means for allowing the flood intake of sea water; and, blow-off means for providing rapid evacuation of the sea water.

References Cited UNITED STATES PATEI` TS 1,201,051 10/1916 Jack 114-0.5 2,359,366 10/1944 Katcher et al. 114-235 2,631,558 3/1953 Harris 114-0.5 3,085,533 4/1963 Goryl et yal 114-74 3,254,620 6/1966 Cannon 114-0.5

MILTON BUCHLER, Primary Examiner.

T. M. BLIX, Assistant Examiner. 

